The present invention relates to a fine particle arranging method, and a liquid crystal display and an anisotropic conductive film obtained by such a method.
Along with the development of the electronics technology, fine particles have come to be widely used in various fields. With respect to such fine particles, for example, conductive fine particles used for anisotropic conductive films, etc., conductive fine particles used in the field of bonding technology and fine particles used for spacers, etc. in liquid crystal displays are listed. Liquid crystal displays form one of the major fields for the application of the fine particles, and the liquid crystal displays have been widely used, for example, in personal computers, portable electronic devices, etc. In general, as illustrated FIG. 11, the liquid crystal display comprises with two substrates 1 provided with a color filter 4, a black matrix 5, a transparent electrode 3, an alignment film 9 thereon, etc. and a liquid crystal 7 interpolated between these two substrates 1. In this case, the members regulating the gap between the two substrates 1 so as to properly maintain the thickness of the liquid crystal layer are spacers 8.
In a conventional manufacturing method for liquid crystal displays, spacers are sprayed uniformly and at random on a substrate bearing pixel electrodes; therefore, as illustrated in FIG. 11, spacers tend to be placed on the pixel electrodes, that is, on the display section of the liquid crystal display. The spacers are generally formed by a material such as a synthetic resin and glass, and if such spacers are placed on the pixel electrodes, the spacer portions tend to cause light leakage due to depolarization effect. Moreover, light void occurs due to the disturbance of the orientation of the liquid crystal on the spacer surfaces, resulting in degradation in contrast and color tones, and subsequent degradation in the display quality.
In order to solve the above-mentioned problem, an attempt is made to place the spacers only on the black matrix portions that form light-shielding films. The black matrix is provided in order to improve the display contrast of the liquid crystal display and, in the case of the TFT-type liquid crystal display, to prevent the elements from malfunctioning optically due to external light.
With respect to the technique for placing the spacers only on the black matrix portions, that is, portions other than the pixel electrodes of the liquid crystal display, Japanese Kokai Publication Hei-4-256925 discloses a method which comprises holding the gate electrode and the drain electrode at the same electric potential at the time of spraying the spacers. Moreover, Japanese Kokai Publication Hei-5-53121 discloses a method which comprises applying a voltage to the wiring electrodes at the time of spraying the spacers. Furthermore, Japanese Kokai Publication Hei-5-61052 discloses a method which comprises applying a positive voltage to the wiring electrodes with the spacers being negatively charged and sprayed in a dry system.
However, all of these methods are arranging techniques that utilize the wiring electrodes. In other words, all of these methods are designed to deal with the TFT-type liquid crystal display in the classification of liquid crystal displays. Therefore, these arranging techniques are not applied to the STN-type liquid crystal display which has no electrodes corresponding to the wiring electrodes and in which striped electrodes, as they are, form pixel electrodes by being arranged orthogonal to each other on upper and lower substrates.
In the liquid crystal display, the necessity of arranging the spacers (one kind of fine particles) on accurate positions has been described above, and in the other fields of the application of fine particles, techniques for arranging fine particles on accurate positions have been demanded. For example, in the case that an anisotropic conductive film is manufactured by using conductive fine particles, it is also necessary to accurately arrange the conductive fine particles so as to obtain an accurate anisotropy and to prevent short-circuiting in the lateral direction.
Here, with respect to techniques for controlling the arrangement of fine particles, techniques such as an electrostatic powder coating method, which comprises forming a coated film by charged fine particles in a state where electric lines of force are formed between the discharging portion of the corona discharge gun or tribo-gun and a target to be coated, have been known.
However, even if charged fine particles are sprayed on fine electrodes by using the corona discharge gun or the tribo-gun, it is difficult to provide accurate control of the arrangement, and even with the application of these techniques, it is difficult to accurately control the arrangement of spacers in manufacturing liquid crystal displays and to manufacture anisotropic conductive films with high performances.
The objective of the present invention is to solve the above-mentioned problems, thus to provide a fine particle arranging method in which the arrangement of fine particles can be accurately controlled, a liquid crystal display and an anisotropic conductive film which are obtained by using said method.
The first invention is a fine particle arranging method which comprises arranging charged fine particles on a surface of an object, wherein areas having a relatively high electric potential (+(positive)) and areas having a relatively low electric potential (xe2x88x92(negative)) are alternately formed on said surface of the object, electric lines of force are formed based upon the areas having the relatively high electric potential (+(positive)) and the areas having the relatively low electric potential (xe2x88x92(negative)), and the fine particles are arranged at relatively +(positive) bottom (1) positions and/or relatively xe2x88x92(negative) bottom (2) positions of said electric lines of force.
The second invention is a fine particle arranging method which comprises arranging fine particles on portions other than the electrodes on the surface of an object by spraying charged fine particles on the object constituted by aligning plural electrodes on the surface thereof, wherein spraying said fine particles is carried out while areas having a relatively high electric potential (+(positive)) and areas having a relatively low electric potential (xe2x88x92(negative)) are alternately formed on said electrode by applying voltages having different voltage values onto the plural aligned electrodes, and applying said voltages having different voltage values is carried out based upon a constant application pattern in which at least one of a relatively +(positive) bottom (1) position and a relatively xe2x88x92(negative) bottom (2) position of electric lines of force is made coincident with a gap position between said plural electrodes, said electric lines of force being formed based upon the voltages having different voltage values applied to the plural electrodes.
The third invention is a fine particle arranging method which comprises arranging fine particles on electrodes by spraying charged fine particles on an object constituted by aligning plural electrodes on the surface thereof, wherein spraying said fine particles is carried out while areas having a relatively high electric potential (+(positive)) and areas having a relatively low electric potential (xe2x88x92(negative)) are alternately formed by applying voltages having different voltage values onto the plural aligned linear electrodes, and applying the voltages having different voltage values is carried out based upon a constant application pattern in which at least one of a relatively +(positive) bottom (1) position and a relatively xe2x88x92(negative) bottom (2) position of electric lines of force is made coincident with a position on said electrode, said electric lines of force being formed based upon the voltages having different voltage values applied to plural electrodes.